This application relates generally to steering columns and more particularly to a crash responsive energy absorbing device for a steering column.
Many steering column assemblies today are equipped with kinetic energy absorption devices to reduce the likelihood of injury in case of an accident. Such devices come in many different forms. One form that is particularly effective in absorbing significant quantities of energy in a relatively small amount of space employs a plastically deformable member such as a metal strap which is bent over a displacement member such as an anvil. In the event of a head-on collision, the strap is drawn across the anvil and causes a reaction force resisting collapse of the steering column and absorbing energy.
Typically energy absorbing devices, such as those employing a plastically deformable strap, are designed to protect drivers of average weight in a collision of average severity, without taking into account the fact that all drivers are not of average weight and that collisions vary considerably in severity depending on vehicle speed at the time of the impact.
In accordance with the present invention, it is possible to vary the reaction force resisting collapse of the steering column. For example, the energy absorbing device of this invention may provide a smaller amount of resistance in the case of a less severe collision or a driver of less than average weight, or a greater amount of resistance in the case of a more severe collision or a driver of more than average weight.
The resistance to steering column collapse is preferably provided by a plastically deformable strap. In one form of this invention, the strap is drawn across a supporting track when the steering column collapses. A displacement member displaces a portion of the strap as it moves along the track to impose a reaction force and absorb energy. More specifically, the displacement member is in the form of a ball located in a pocket on the strap-supporting surface of the track.
In a preferred form of the invention, not only one but a plurality of balls of differing diameter are provided, with an actuator for moving one of the balls into position to serve as the displacement member. The greater the diameter of the ball, the greater the deformation of the strap and thus the greater the amount of energy absorbed by the strap when the steering column collapses. A smaller diameter ball will result in less deformation of the strap and thus less energy absorption.
A controller is provided to monitor and detect such conditions as vehicle speed, driver weight, driver seat position and whether or not the driver is belted, and with that information determine how much energy is desired to be absorbed and accordingly how much resistance to strap movement is required and therefore which of the balls is to be selected as the displacement member. The actuator is operated by a signal from the controller through a fast-acting solenoid or pyrotechnic device which will operate the actuator in only milliseconds after the signal is received.
In another form of the invention, the strap has a laterally displaced curved portion of generally U-shape into which an anvil extends. The curved portion of the strap is displaced a predetermined distance depending on the laterally adjusted position of the anvil. When the strap is moved across the anvil, the U-shape travels along the length of the strap to absorb energy. The magnitude of the resistance to movement of the strap across the anvil is dependent upon the laterally displaced position of the U-shaped portion of the strap and that is determined by the laterally adjusted position of the anvil. The anvil is laterally adjusted by an actuator which responds to a signal from a controller which monitors the conditions previously referred to.
One object of this invention is to provide an energy absorbing device having the foregoing features and capabilities.
Other objects, features and advantages of the invention will become more apparent as this description proceeds.